1. Field of the Invention
The invention relates to a system for transferring fluids from a piping system which is firmly connected with a ship's hull, to a turning device, and vice versa, in which the turning device is rotatably connected with said hull and adapted to be anchored to the sea floor and to be connected with at least one flexible riser, which is connected with respective devices that are firmly connected with the sea floor and with hoses which are connected with tanks in said hull, via a manifold for each riser provided on the upper portion of the turning device.
2. Description of the Prior Art
Systems of this kind are used in production of oil and gas from offshore fields. The vessel could, alternatively, be firmly anchored to the sea floor, being all the time maintained above the gas or oil well with its longitudinal axis directed the same way.
Great forces to which anchoring means are subjected when a vessel lies across the wind and wave direction, however, make such anchoring difficult. This is avoided by, in stead, anchoring the vessel, via a turning device or turntable which is provided substantially midship and can turn about a vertical axis relative to the ship's hull, and which is firmly anchored to the sea floor by the aid of, e.g. chains extending radially away from the turntable and down to the sea floor, so that the turntable cannot rotate about its vertical axis relative to the sea floor. The vessel is made vane stable, so that it will automatically seek to find a position with its bow facing the wind. In order to transfer oil and gas from the wells to the tanks in said hull, there are provided flexible risers which connect the well with the turntable, and hoses which permanently connect the turntable with the tanks, said hoses during rotation of the vessel due to changing wind being wound about the turntable. Due to the large diameter (approximately 25 m) of the turntable, and the weight and diameter of hoses, the hose length is limited which, in turn, limits the total mutual rotation of the turning device and the hull to approximately 360.degree.. If, however, the vessel turned over said angle, and the weather will probably cause further rotation, the vessel must be turned in the opposite direction, e.g. by the aid of a thruster to unwind the hoses from the turntable. During such operations the vessel will periodically have its broadside against the wind. Since the vessel is connected with the wells and production goes on during such turning operations, it will be obvious that such a maneuver is most hazardious, especially if the wave height and the wind velocity are high.